This invention relates to the control of a contaminant cleaning apparatus, particularly with regard to clearing rails of snow.
The use of compressed air to clean the rail in a railroad system goes back to the 1800s. The cleaning of the rail is very important for better adhesion performance between the locomotive wheel and the rail. There is a need for a rail cleaning system that effectively minimizes the on-time of the rail cleaning device to reduce air compressor wear by disabling the device when it is not needed. There is a need for the rail cleaning system to recognize the conditions during which the system should be engaged. The system should also be capable of learning whether it should be on or off as conditions change.
U.S. Pat. No. 77,602 issued on May 5, 1868 to Floyd describes the use of steam from the boiler of a locomotive that is directed onto the rails prior to the traction wheels of the locomotive. This steam blows and melts any snow or ice off the rails prior to contact by the traction wheels to the rails, thus improving the grip of the wheels onto the rails.
U.S. Pat. No. 2,597,719 by Foster, issued on May 20, 1952, describes a track cleaning apparatus mounted to a locomotive to effectively remove all foreign matter that may accumulate on the rails in advance of the traction wheels, particularly snow. The purpose is to clean the rails of bulk contaminants for the purpose of getting sand directly on top of the rail in position for effective contact between the wheel and the rail. Foster describes a system of blowing heated air and heated compressed air directly onto the tracks to melt the snow or ice and removal of the snow or ice.
Locomotives and transit vehicles as well as other large traction vehicles are commonly powered by electric traction motors coupled in driving relationship to one or more axles of the vehicle. Locomotives and transit vehicles generally have at least four axle-wheel sets per vehicle with each axle-wheel set being connected via suitable gearing to the shaft of a separate electric motor commonly referred to as a traction motor. In the motoring mode of operation, the traction motors are supplied with electric current from a controllable source of electric power (e.g., an engine-driven traction alternator) and apply torque to the vehicle wheels which exert tangential force or tractive effort on the surface on which the vehicle is traveling (e.g., the parallel steel rails of a railroad track), thereby propelling the vehicle in a desired direction along the right of way. Good adhesion between each wheel and the surface is required for efficient operation of the vehicle.
It is well known that maximum tractive or braking effort is obtained if each powered wheel of the vehicle is rotating at such an angular velocity that its actual peripheral speed is slightly higher (motoring) than the true vehicle speed (i.e., the linear speed at which the vehicle is traveling, usually referred to as "ground speed" or "track speed"). The difference between wheel speed and track speed is referred to as "creepage" or "creep speed." There is a variable value of creepage at which peak tractive effort is realized. This value, commonly known as the optimal creep setpoint is a variable that depends on track speed and rail conditions. So long as the allowable creepage is not exceeded, this controlled wheel slip is normal and the vehicle will operate in a stable microslip or creeping mode. If wheel-to-rail adhesion tends to be reduced or lost, some or all of the vehicle wheels may slip excessively, i.e., the actual creep speed may be greater than the maximum creep speed. Such a gross wheel slip condition, which is characterized in the motoring mode by one or more spinning axle-wheel sets, can cause accelerated wheel wear, rail damage, high mechanical stresses in the drive components of the propulsion system, and an undesirable decrease of tractive effort.
The peak tractive effort limits the pulling/braking capability of the locomotive. This peak tractive effort is a function of various parameters, such as weight of the locomotive per axle, wheel rail material and geometry, and contaminants like snow, water, grease, insects and rust. Contaminants in the wheel/rail interface reduce the maximum adhesion available, even at the optimal creep setpoint.
In a normal motoring or propulsion mode of operation, the value of the engine speed call signal is determined by the position of a handle of a manually operated throttle. A locomotive throttle conventionally has eight power positions or notches (N), plus idle and shutdown. N1 corresponds to a minimum desired engine speed (power), while N8 corresponds to maximum speed and full power. In a consist of two or more locomotives, only the lead unit is usually attended, and the controller onboard each trail unit will receive, over a trainline, an encoded signal that indicates the throttle position selected by the operator in the lead unit. The eight discrete power notches described above may be replaced by a continuously variable controller. For each power level of the engine, there is a corresponding desired load.